Optical and electrical characteristics of Ga-Zn-O thin films prepared by RF magnetron co-sputtering system

Abstract

We investigated the optical, electrical, and structural properties of GaZnO (GZO) thin films which have proven the potential uses in transparent thin film transistor. The doping concentrations of Ga atoms in GZO thin films were continuously controlled via the RF magnetron co-sputtering system in which ZnO target was sputtered at a fixed RF power 200 W, while Ga2O3 target was sputtered with a varied RF power from 30 W to 100 W. The highest electrical conductance and carrier mobility coincides with the dramatic optical band gap widening due to Burstein-Moss effect at the ∼3% atomic concentration of Ga doping. This study clearly indicates that the number of degenerate electrons in the conduction band increases sharply near the 3% doping level, but the band narrowing effect begins to dominate due to the electron-electron and electron-impurity interactions, resulting in the decrease of the carrier mobility beyond the optimized doping level.